This invention relates to compositions comprising a flammable material and a flame retardant. More especially, it relates to compositions comprising macromolecular flammable materials, for example, polymers. The invention also relates to flame retardants and a process for their manufacture.
The problem of the flammability of certain materials has received considerable attention. One method by which the flammability of certain materials, especially macromolecular materials, has been reduced is by the incorporation therein of halogen-containing compounds, both inorganic and organic. Inorganic halogen-containing compounds often have deleterious effects on the properties of the materials, or damage the equipment in which the materials are processed, because of their corrosive nature, and therefore organic halogen-containing compounds, often in combination with inorganic oxides or non-halogenated salts, have been used most extensively.
While the previously proposed organic halogen-containing compounds have been accepted, many disadvantages are still associated with their use. Many previously proposed flame retardants have been more or less volatile, leading to loss in flame retardance during use of articles containing them, as well as in processing. As macromolecular materials having higher use temperatures (and, accordingly, higher processing temperatures) have been developed, the disadvantages of volatile additives become more marked. In addition, such higher use and processing temperatures have shown up deficiencies in the thermal stability of many of these previously proposed organic halogen-containing flame retardants. Thus, many compounds which have been readily incorporated in materials processed at 150.degree. C. have failed due to volatilization, sublimation or decomposition when incorporated into a material which is processed at temperatures in the region of 250.degree. C. to 350.degree. C. Further, some of the commercial materials are adversely affected by the radiation making them unsuitable for incorporation into compositions which are to be irradiation crosslinked.
Some additives may, for example, be sensitive to water even when incorporated into the material, and when additive-containing compositions are tested with boiling water, the organic compound is dissolved out or hydrolyzed, resulting at best in impaired flame retardance, and often also in corrosion by the hydrolysis products, for example, the halogen acids, resulting from contact with water. Such water sensitivity also shows when the composition is in prolonged contact with a humid atmosphere.